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How to find the velocity of the protons and antiprotons?

  1. Apr 28, 2012 #1
    1. The problem statement, all variables and given/known data

    Some particle accelerators allow protons (p+) and antiprotons (p-) to circulate at equal speeds in opposite directions in a device called a storage ring. The particle beams cross each other at various points to cause p+ + p- collisions. In one collision, the outcome is p+ + p- yields e+ + e- + γ + γ, where γ represents a high energy gamma-ray photon. The electron and position are ejected from the collision at 0.9999995c and the gamma-ray photon wavelengths are found to be 1.0 X 10-6 nm. What were the proton and antiproton speeds prior to the collision?

    m(e-)=9.11e-31(kg), λ(γ)=1e-6(nm)



    2. Relevant equations
    Ei = Ef
    E=mc^2 - 0.5mu^2
    E=γmc^2


    3. The attempt at a solution
    I have no ideas how to start and where to start in this question. Please help.
     
  2. jcsd
  3. Apr 28, 2012 #2

    tiny-tim

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    hi yy205001! :smile:

    (try using the X2 button just above the Reply box :wink:)

    conservation of energy?
     
  4. Apr 28, 2012 #3
    i dont know what does'' p+ + p- yields e+ + e- + γ + γ'' tell me?
     
  5. Apr 29, 2012 #4

    tiny-tim

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    well, you know the mass of everything, and you know the wavelength of the photons, and the speed of the electrons
     
  6. Apr 30, 2012 #5
    but how can we get the mass of the gamma ray?
     
  7. Apr 30, 2012 #6

    tiny-tim

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    the gamma ray is a photon, with zero mass :wink:
     
  8. May 1, 2012 #7
    oh!! thank you=]
     
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